I think altruism isn’t directly evolutionarily connected to power, and it’s more like “act morally (according to local culture) while that’s helpful for gaining power” which translates to “act altruistically while that’s helpful for gaining power” in cultures that emphasize altruism. Does this make more sense?
I think that there is a version of an altruistic pursuit where one will, by default, “reduce his power.” I think this scenario happens when, in the process of attempting to do good, one exposes himself more to unintended consequences. The person who sacrifices will reduce his ability to exercise power, but he may regain or supersede such loss if the tribe agrees with his rationale for such sacrifice.
I think that there is a version of an altruistic pursuit where one will, by default, “reduce his power.” I think this scenario happens when, in the process of attempting to do good, one exposes himself more to unintended consequences. The person who sacrifices will reduce his ability to exercise power, but he may regain or supersede such loss if the tribe agrees with his rationale for such sacrifice.